The invention relates to a method for the manufacture of a shaft having a larger diameter flange, particularly for a cone gear.
A method is known from DE 195 32 519 C2, in which a step is formed on a shaft by flow-forming so as to give a larger diameter retaining flange. However, as a result of the method, flow-forming can only lead to relatively small diameter increases.
DE 42 25 364 A1 discloses so-called bore or hole spinning, in which punches are spun in a solid workpiece. For forming a hollow body spinning rolls and annular tools are infed and bring about an axial material flow, while preventing a diameter increase.
A cone gear is e.g. described in EP 222 929 A1. Two pulleys located on a shaft can be displaced axially with respect to one another so that as a result of the relative displacement a driving belt, such as a V-belt, can penetrate to a greater or lesser extent between the conical pulleys. Therefore the belt can engage with different diameters of the arrangement, so that it is possible to modify the transmission ratio of a belt pulley drive.
In the case of cone gears in general one pulley is firmly connected to a shaft, so that in particular it cannot be axially displaced. The other pulley is displaceable, so that an axial spacing change can take place.
Different methods are known for the manufacture of cone gears. It is, for example, conceivable to construct the pulley firmly connected to the shaft as a separate component and to fit it to the shaft using fastening means. The fixed pulley can also be connected to the shaft by a welding process. However, such multipart constructions of shaft and pulley are expensive to manufacture. In addition, the position of the arrangement joined by fastening means or the weld point is subject to stress during the operation of the gear as a result of the power transmission to or from the shaft, so that here again disadvantages arise. It is consequently appropriate to manufacture the arrangement constituted by the shaft and the fixed pulley in one piece. For this purpose forging or casting processes are usable, but are relatively complicated and expensive. In addition, the attainable maximum difference between a maximum and a minimum size power transmission diameter is greatly limited, particularly in the case of manufacture by a forging process.
Therefore the object of the invention is to so further develop a method of the aforementioned type that the arrangement of shaft and flange can be manufactured in a particularly economic manner, the flange diameter being variable over a wide range.
According to the invention this object is achieved in that a round stock as the workpiece is rotated about its longitudinal axis relative to at least one spinning roll and is upset in the axial direction and that the material displaced during axial upsetting is formed to the larger diameter flange under the action of the at least one spinning roll. The flow-forming process offers the possibility of constructing in one piece the arrangement of the shaft and flange, the flange in the case of a cone gear being used as a conical pulley, whilst also permitting a larger diameter variation with respect to the power transmission point of a gear. As a result of the axial upsetting of the starting workpiece the radial material flow is assisted in coordination with the action of the spinning roll. Even though the method is preferred for the manufacture of a part of a so-called cone gear, it can also be used for the manufacture of random shafts having a flange.
Preferably to the workpiece is infed at least one spinning roll pair with two spinning rolls, which are mutually axially spaced and the flange is formed between the two spinning rolls. This leads to a clearly defined, radial material flow, both sides of the flange to be formed being fixable with respect to their contour by contact with the particular spinning roll. For a particularly good power distribution it is possible to uniformly circumferentially distribute two, three or more spinning roll pairs.
The workpiece is preferably heated in the area in which the flange is formed and in particular to a temperature above the recrystallization point. As a result of the heating it is possible to perform the working process using lower forces. If a heating to above the recrystallization point takes place, a particularly stable, high quality worked product is obtained and working is not limited by a work hardening. The starting workpiece can be constituted by a solid rod or a pipe, in which during the working process a stiffening mandrel is introduceable into the pipe cavity.
Preferably use is made of one or more spinning rolls with a shoulder, one shoulder face engaging on an approximately axially directed outer circumference of the workpiece, whereas the other shoulder face passes approximately radially corresponding to the flange to be formed. Thus, the flange is formed on the radially directed shoulder face of the spinning roll, so that the flange shape can be determined by the choice of spinning roll. As a result of the approximately axially directed shoulder face there is a certain guidance of the particular spinning roll by the workpiece.
It can naturally be useful to use at least one spinning roll pair in which at least one spinning roll has a roughly disk-like or sleeve-like construction and if the axis of the disk-like spinning roll is approximately parallel to the longitudinal axis of the workpiece. The use of a disk-like spinning roll is preferred as a particularly simple variant of the method according to the invention. As a result of the parallelism of the roll axis and the workpiece axis, it is possible in simple manner to produce exactly radially oriented flange side faces.
It is particularly preferred if the two spinning rolls of the at least one spinning roll pair are axially fed in against one another for forming the flange. As a result of the axial infeed the material is axially displaced. The flow direction of the displaced material is determined by the joint action of the two rolls, so that the radially extending flange is produced in a clearly defined manner.
Appropriately the axial upsetting and infeeding movements of the at least one spinning roll are controlled in matched manner. As a result of a control a particularly good method sequence can be obtained, which is particularly useful for reducing product tolerances.
In accordance with the present invention, a displaceable cone pulley element is manufactured in one piece from an approximately disk-like starting workpiece by flow-forming. The advantages of the flow-forming of gear elements were described in conjunction with the manufacture of the flange firmly connected to the shaft. It is also advantageous that the entirety of the cone gear elements in question can be manufactured with the same basic method. This permits the use of the same materials and a comparable manufacturing technology. In addition to a disk segment it is possible to use as the starting workpiece a forging or casting, which has a certain preliminary shape.
Preferably at least the cylindrical circumferential wall section is flow-formed in a splitting-upsetting process from a radially directed portion of the starting workpiece. As a result of the splitting-upsetting process it is possible to bring about a comparatively large material quantity without the use of excessive forces with an overtravel of a splitting roll. This is economic and leads to particularly high quality workpieces.
Preferably the internal contour in the starting workpiece is formed by an externally toothed spinning chuck. The provision of the internal contour can consequently be integrated into the flow-forming method according to the invention for the manufacture of the displaceable cone pulley element.
Compared with the prior art, a cone gear according to the invention is characterized in that the shaft with the flange is manufactured according to a method or an advantageous development according to the invention or that the displaceable conical pulley element is manufactured according to a method or an advantageous development according to the invention. The inventive advantages of the method are consequently implemented in the cone gear. Particular reference is made to the simplicity of manufacture, the quality of the gear elements and the high transmission ratio of the gear.
The invention is based on the surprising finding that it is possible to manufacture a high quality cone gear by a flow-forming procedure. This is brought about in that the flow movement of the material necessary for forming a flange is assisted by an axial upsetting of the starting workpiece. It is also particularly stressed that all the gear parts described can be manufactured by a flow-forming procedure, so that the entire production process can take place with the same technology and consequently remains in the same hands. Obviously the invention is not restricted to elements of cone gears. For example, a shaft manufactured according to the invention with a flange can be used in various gears. In addition, the worked part produced need not be a shaft. It is in fact possible to manufacture random parts with a circumferential flange.